X-ray scanners, such as are used by airport authorities for checking luggage, are increasingly important in the fight against international terrorism. It is current policy at many airports to check not only cargo luggage but hand luggage also using X-ray scanners in order to locate the presence in a passenger's luggage of explosives, firearms and other ammunition.
Clearly, the effectiveness of such scanners depends upon the experience and expertise of the operator. X-ray scanners operate by passing the luggage along a conveyer belt through an X-ray machine which produces a visual image of the contents of the luggage on a suitable display unit. The operator can, and will, stop the conveyer belt in order to examine the contents of a particular piece of luggage and can also zoom in on a particular area of the screen in order to check an identified area more closely.
On account of the increasing passenger throughput at major airports, it has become increasingly necessary to process passenger luggage quickly. This requirement often militates against efficiency and, at worst, is responsible for the successful attempts in recent years by terrorists to smuggle bombs and explosives in their luggage.
Up till now, airport security personnel using X-ray scanners have developed their expertise through experience and through learning from more experienced operators. Since it takes very many years indeed to acquire the necessary expertise and since, moreover, terrorists are themselves developing more sophisticated methods of hiding firearms and so on in their luggage, it is not always easy for even experienced operators to be one step ahead of the terrorist and traditional methods of teaching novices are, at best, cumbersome.
Simulators for simulating moving images are, of course, known. Generally, such simulators employ animation techniques for producing a moving image based either on video processing or graphics techniques.
Video processing techniques require that a moving object is photographed very rapidly so as to produce at least 30 still images of the moving object each second. The still images, or frames, are then displayed on a suitable display screen whereby the impression of flicker-free continuous movement is achieved owing to the eyes' persistence of vision. A drawback with such techniques when used with computer-based simulators is that a very large volume of computer memory is required in order to store all the frames of image data. Thus, if for each second of vision time there are required 30 frames of image data, it is clear that to simulate a moving image for even a short period of time can require prohibitively large amounts of memory.
Graphics techniques require that a still image be digitized into the computer's memory which is itself a highly skilled, time-consuming and consequently expensive process. Once stored within the computer memory, the computer itself may be programmed to generate successive frames of image data whose rapid display creates the impression of movement in a similar manner to the video technique described above.
Consequently, both of the standard prior art techniques for creating moving images are expensive, either owing to the large volume of memory required or owing to the digitization of a stationary image.